Signal processors for matching signal patterns such as speech signal patterns or visual signal patterns are known. For example, U.S. Pat. No. 4,181,821; issued Jan. 1, 1980 entitled "Multiple Template Speech Recognition System;" discloses a processor for matching, or recognizing, an unknown speech signal as one of a set of reference signals. In known speech recognition systems, an input speech signal representing an audible utterance is analyzed to provide a set of feature signals which characterize the utterance. Such feature signals may typically be derived from spectral analysis or linear prediction analysis of the utterance. Initially, the recognition system apparatus is trained through the use of input utterances of identified reference words. Each input utterance of a known, identified word is analyzed to provide a set of reference feature signals, which reference signals are stored. Subsequent to the storage of a set of reference signals for each reference word to be recognized by the system, an unknown utterance is analyzed and a set of feature signals representative of the unknown utterance is obtained. The unknown utterance feature signals are compared with the sets of stored reference feature signals to determine the correspondence or degree of dissimilarity or similarity therebetween. After the comparisons are completed, the unknown utterance is identified as the reference signal whose feature signals most closely correspond to the feature signals of the unknown utterance.
As to a signal comparison technique, dynamic programming is a technique which is known for solving various optimization problems. Dynamic programming can also be used for time warping, e.g., one signal may be non-linearly stretched or compressed in either time or space to optimally match another signal. Signal processors, which have an architecture for allowing efficient solution of such dynamic time warping problems through the use of parallel processing, are known. For example, a copending application by the instant applicants, i.e., Ser. No. 245,952 now U.S. Pat. No. 4,384,273; entitled "Time Warp Signal Recognition Processor for Matching Signal Patterns" and filed Mar. 20, 1981, discloses a signal processor which includes an orthogonal array of processor cells. Each cell is connected to its nearest neighboring cells (i.e., to its nearest upward cell and to its nearest rightward cell). Also, each cell can be structurally similar to each and every other cell. More particularly, data are synchronously extended in a left-to-right as well as in a bottom-to-top direction by means of data channels. As the data are so extended, the signal processor generates a measure of the correspondence between the input signals. In generating the correspondence measure, the processor includes an arrangement for controlling all processor cells on a predetermined diagonal of the array of cells. Thereby all cells coupled to the predetermined diagonal can operate in parallel to increase the efficiency of the signal processor. Also, not only can all cells on each diagonal operate in parallel but also one or more of the plurality of diagonals can operate as a group and in parallel for processing the same or different sets of input signals.
This combination of data and control information flow jointly with the orthogonal array of processor cells comprises a structure capable of efficiently solving a class of pattern matching problems such as may occur in a speech signal or visual signal recognition system. However, known signal processors tend to contemplate many processor cells and hence tend to be expensive.